Clinicians require medical information, and in particular medical display images, to be presented in a manner which enables medical information to be interpreted accurately and quickly.
Certain type of medical images may be associated with a standard format familiar to all clinicians. For example, X-ray images conventionally have a dark or black background and white/grey images corresponding to a subject's tissues. In contrast, in some cases, it may be advantageous for text or graphic information, or shaded volume rendered images, to be displayed with a light background.
Several types of medical image may be viewed at one time, and the dominant background tones of different types of medical image may be incompatible, due to the glare and contrast effects. For example, a very bright image (e.g. having a predominately white background) may impair interpretation of adjacent darker images (e.g. greyscale images on a predominately dark background), and vice versa.
In addition, it may be necessary for medical images to be viewed in either relatively bright or relatively dark environments, as dictated for example by ambient light conditions in hospital wards, operating theatres or instrument suites. Ambient light conditions may not be optimal for viewing medical images. For example, it may be more difficult for a clinician to interpret a medical image having a predominately a white or bright background in a darkened room than it would be to interpret the same image in a well lit room.
FIG. 1 illustrates how contrast effects can influence the visual interpretation of data. The mid-grey tone of rectangle 1 is perceived by at least some people as being lighter when displayed on a dark grey background 2, than when displayed on a light grey background 3.
When interpreting medical data, in particular medical images, effects of this type can lead to errors, delays or eye fatigue.
FIGS. 2a and 2b show a medical display 10, which includes a shaded volume rendered (SVR) image 12 of a human pelvis derived from CT data, adjacent to three multi-planar reformatted (MPR) images 14, 16, 18 derived from the CT data. Glare and contrast effects caused by the much brighter SVR image 12 makes the darker MPR images more difficult to interpret, particularly in a darkened instrument room. FIG. 2b is a representative line-drawn version of FIG. 2a, but with all backgrounds shown in white.
Changing the format of an image may alleviate contrast effects, but images displayed in an unconventional format may be more difficult for clinicians to interpret. For example, the white background of the SVR image 12 of FIG. 2a may be changed to a black background for consistency with the MPR images. However, whereas glare and contrast effects are reduced, fine structure of the SVR image cannot be clearly seen on a black background.
As a compromise, the SVR image 12 could be displayed on a grey background. However, some fine structure of the compromise SVR image remains difficult or impossible to decipher and the glare/contrast effects on adjacent MPR images are reduced only to some extent.